Field of the Invention
The present invention relates to wireless communication, and more particularly, to an interference alleviation method performed by a first base station in a wireless communication system including a first base station and a second base station using adjacent resources, and an apparatus using the method.
Related Art
Long-Term Evolution (LTE) is a mobile communication standard based on 3rd Generation Partnership Project (3GPP) Technical Specification (TS) Release 8, LTE-Advanced (LTE-A) is a mobile communication standard and an enhancement of the LTE standard.
LTE-A supports carrier aggregation in which a plurality of carriers is aggregated and set to be used for a single user equipment (UE). Carrier aggregation conventionally supports aggregation of frequency division duplex (FDD) cells using an FDD frame and aggregation of time division duplex (TDD) cells using a TDD frame only. However, carrier aggregation has also support aggregation of FDD cells and TDD cells and aggregation of TDD cells having different uplink-downlink configurations in recent years. An uplink-downlink configuration is setting information indicating which among an uplink subframe, a downlink subframe, and a special subframe each subframe in a TDD frame is.
A plurality of channels in the same frequency band may be positioned close or adjacent to each other on the frequency axis. Communications in different directions may be performed on the adjacent channels. For example, suppose that TDD cells using different uplink-downlink configurations are aggregated and at least two TDD cells are located in the same frequency band.
In this case, there may be a subframe in which one cell performs downlink transmission from a base station (BS) to a UE at a first frequency and another cell performs uplink transmission from a UE to a BS at a second frequency. If the first and second frequencies are adjacent or close to each other, the two transmissions cause interference to each other, thus deteriorating performance.
Such a problem may arise even not in a carrier aggregation situation. For example, when a first BS operated by a first operator and a second BS operated by a second operator perform communications in different directions in all or some of overlapping subframes, the communications cause interference to each other.
Thus, there is a need for a method for mitigating mutual interference between BSs or cells that perform communications in different directions using adjacent resources.